DE102010012374A1 - High-voltage electrolytic capacitors - Google Patents

Abstract

A liquid electrolytic capacitor is provided which comprises a porous anode body containing a dielectric layer formed by anodic oxidation, a cathode comprising a metal substrate coated with a conductive polymer, and an aqueous electrolyte in contact with the cathode and the cathode Anode includes. The electrolyte comprises a salt of a weak organic acid and water. The electrolyte has a pH of about 5.0 to about 8.0 and an ionic conductivity of about 0.5 to about 80 milli-millions per centimeter or more, determined at a temperature of 25 ° C.

Description

Background of the invention

electrolytic capacitors typically have a larger capacity per unit volume than certain other types of capacitors, which is why they are valuable in electrical circuits with relatively high levels Amperages and low frequency are. A type of capacitor, which was developed is a "liquid" electrolytic capacitor, comprising an anode of sintered tantalum powder. These tantalum sintered bodies have a very large inner surface. These Tantalum sintered bodies first undergo an electrochemical Oxidation, which acts as a dielectric oxide coating over the entire outer and inner surface of the Forms tantalum bodies. Then the anodized tantalum sintered bodies enclosed in cups that are a highly conductive and contain corrosive liquid electrolyte solution and a large surface with conductive Have linings, which the flow of current to the liquid Allow electrolyte solution.

The electrolyte solutions used in tantalum liquid electrolytic capacitors conventionally consist of one or two basic preparations. The first preparation consists of an aqueous solution of lithium chloride. The second electrolyte preparation conventionally used in tantalum liquid condensers consists of a 35-40% aqueous solution of sulfuric acid. Although corrosive, such a sulfuric acid electrolyte has a low resistivity, a wide temperature capability, and a relatively high maximum working voltage, and thus is the electrolyte of choice for the vast majority of conventional tantalum liquid capacitors. However, there have been efforts to develop other electrolytes for liquid capacitors. The U.S. Patent No. 6,219,222 (Shah et al.) Describes, for example, an electrolyte employing a solvent system comprising water and ethylene glycol as well as an ammonium salt. Shah et al. indicate that the electrolyte has a high conductivity and breakdown voltage, so that the equivalent series resistance is lowered. Unfortunately, the problems persist that such capacitors still have difficulty achieving high voltage levels.

Therefore there is currently a need for an improved liquid electrolytic capacitor, which can reach a high voltage.

Brief description of the invention

According to one Embodiment of the present invention is an electrolytic capacitor discloses, comprising: a porous anode body, the one formed by anodic oxidation dielectric layer contains; a cathode comprising a metal substrate, coated with a conductive polymer; and an aqueous electrolyte in contact with the Cathode and the anode is located. The electrolyte comprises a salt a weak organic acid and an aqueous Solvent. The electrolyte has a pH of about 4.5 to about 7.0 and an ionic conductivity of about 0.1 to about 30 millisiemens per centimeter, determined at a temperature from 25 ° C.

Further Features and aspects of the present invention are as follows set out in more detail.

Brief description of the drawings

in the Rest of the description, where reference is made to the attached figure is taken is a directed to the skilled person complete and reworkable disclosure of the present invention including their best realization; where is:

1 a cross-sectional view of an embodiment of a capacitor formed according to the present invention.

at multiple use of reference numerals in the present specification and the drawings are intended to have the same or analogous features or represent elements of the present invention.

Detailed description of representative embodiments

Those skilled in the art should be aware that the present discussion is only a description of exemplary embodiments and not the broader aspects of the present invention which broader aspects are embodied in the exemplary construction.

Generally said, the present invention relates to an electrolytic capacitor, a porous anode body having a dielectric Layer contains a cathode containing a metal substrate, which is coated with a conductive polymer, and an aqueous electrolyte. The ionic conductivity the electrolyte is targeted within a certain range controlled so that the capacitor is charged up to a high voltage can be. In particular, the electrolyte typically has one Ionic conductivity of about 0.1 to about 30 millisiemens per centimeter ("mS / cm"), in some embodiments from about 0.5 to about 25 mS / cm, in some embodiments about 1 to about 20 mS / cm, and in some embodiments, about 2 to about 15 mS / cm, determined at a temperature of 25 ° C and using any known meter for the electrical conductivity (eg Oakton Con Series 11). Within the above ranges, the Ion conductivity of the electrolyte presumably that the electric field sufficiently far (Debye length) in extends into the liquid electrolyte so that it a significant charge separation occurs. This becomes the potential energy of the dielectric extended to the electrolyte, so that the resulting Capacitor can save even more potential energy than it due the thickness of the oxide dielectric layer is predicted. With In other words, the capacitor can be charged up to a voltage which exceeds the formation voltage of the dielectric. The ratio of the voltage, up to that of the capacitor can be charged, for example, to the formation voltage 1.0 to 2.0, in some embodiments, about 1.1 to about 1.8 and in some embodiments about 1.2 to about 1.6. As an example, the tension, up to that of Capacitor is charged, about 200 to about 350 V, in some Embodiments about 220 to about 320 V and in some Embodiments about 250 to about 300 V.

The ionic conductivity of the electrolyte is achieved, in part, by selecting a particular type of salt within a particular concentration range. The inventors have found that salts of weak organic acids are particularly effective in achieving the desired conductivity of the electrolyte. The cation of the salt can be monatomic cations, such as alkali metals (eg Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ or Cs ⁺ ), alkaline earth metals (eg Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ or Ba ²⁺ ), transition metals (eg, Ag ⁺ , Fe ²⁺ , Fe ³⁺ , etc.) and polyatomic cations, such as NH ₄ ⁺ . The monovalent ammonium (NH ₄ ⁺ ), sodium (K ⁺ ) and lithium (Li ⁺ ) are particularly suitable cations for use in the present invention. The organic acid used to form the anion of the salt is "weak" in the sense that it typically has a first acid dissociation constant (pK _a1 ) of about 0 to about 11, in some embodiments about 1 to about 10, and in some embodiments about 2 to about 10, determined at 25 ° C. In the present invention, any suitable weak organic acids may be used, such as carboxylic acids, such as acrylic acid, methacrylic acid, malonic acid, succinic acid, salicylic acid, sulfosalicylic acid, adipic acid, maleic acid, malic acid, oleic acid, bile acid, tartaric acid (e.g., L-tartaric acid, meso-tartaric acid etc.), citric, formic, acetic, glycolic, oxalic, propionic, phthalic, isophthalic, glutaric, gluconic, lactic, aspartic, glutamic, itaconic, trifluoroacetic, barbituric, cinnamic, benzoic, 4-hydroxybenzoic, aminobenzoic, etc., mixtures thereof etc. Polyprotic acids (e.g., diprotic, triprotic, etc.) are particularly desirable for use in the formation of the salt, such as adipic acid (pK _a1 of 4.43 and pK _a2 of 5.41), α-tartaric acid (pK _a1 of 2.98 and pK _a2 of 4.34), meso-tartaric acid (pK _a1 of 3.22 and pK _a2 of 4.82), oxalic acid (pK _a1 of 1.23 u nd pK _a2 of 4.19), lactic acid (pK _a1 of 3.13, pKa ₂ of 4.76 and pK _a3 of 6.40), etc.

The Concentration of salts of weak organic acid in the electrolyte is chosen so that the desired Ion conductivity is achieved. While the actual quantities depending on the particular used Salt, whose solubility in the or in the electrolyte used solvents and the presence of other components may vary, are such salts of a weak organic acid typically in an amount of from about 0.1 to about 25 weight percent, in some embodiments about 0.2 to about 20 wt .-%, in some embodiments about 0.3 to about 15 wt% and in some embodiments about 0.5 to about 5 wt%. present in the electrolyte.

The aqueous electrolyte may generally have a variety of forms such as solution, dispersion, gel, etc. However, regardless of its form, the aqueous electrolyte contains water (eg, deionized water) as a solvent. For example, water (eg, deionized water) may be from about 20% to about 95% by weight, in some embodiments from about 30% to about 90% by weight, and in some embodiments about 40% by weight. % to about 85% by weight of the electrolyte. In certain cases, a secondary solvent may also be used in conjunction with water to form a solvent mixture. Suitable secondary solvents include, for example, glycols (e.g., ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, hexylene glycol, polyethylene glycols, ethoxy diglycol, di propylene glycol, etc.), glycol ethers (e.g., methyl glycol ethers, ethyl glycol ethers, isopropyl glycol ethers, etc.), alcohols (e.g., methanol, ethanol, n-propanol, isopropanol, and butanol), ketones (e.g., acetone, methyl ethyl ketone, and methyl isobutyl ketone ), Esters (e.g., ethyl acetate, butyl acetate, diethylene glycol ether acetate, methoxypropyl acetate, ethylene carbonate, propylene carbonate, etc.), amides (eg, dimethylformamide, dimethylacetamide, dimethylcaprylic / capric fatty acid amide and N-alkylpyrrolidones), sulfoxides or sulfones (e.g. Dimethylsulfoxide (DMSO) and sulfolane), etc. Such solvent mixtures typically contain water in an amount of from about 40% to about 80% by weight, in some embodiments from about 50% to about 75% by weight, and in In some embodiments, about 55 wt% to about 70 wt% and one or more secondary solvents in an amount of about 20 wt% to about 60 wt%, in some embodiments, about 25 wt% to about 50% by weight, and in some embodiments from about 30% to about 45% by weight. For example, the secondary solvent (s) may be from about 5 weight percent to about 45 weight percent, in some embodiments from about 10 weight percent to about 40 weight percent, and in some embodiments, from about 15 weight percent to about Make up 35 wt .-% of the electrolyte.

Of the aqueous electrolyte is also relatively neutral and has a pH of about 4.5 to about 7.0, in some embodiments from about 5.0 to about 6.5, and in some embodiments from about 5.5 to about 6.0. If desired, you can one or more pH regulators (eg acids, bases, etc.) be used so that the desired pH is reached can be. In one embodiment, an acid used to adjust the pH to the desired range to lower. Suitable acids include Example inorganic acids such as hydrochloric acid, Nitric acid, sulfuric acid, phosphoric acid, Polyphosphoric acid, boric acid, boronic acid etc., organic acids including carboxylic acids, such as acrylic acid, methacrylic acid, malonic acid, Succinic acid, salicylic acid, sulfosalicylic acid, Adipic acid, maleic acid, malic acid, oleic acid, Gallic acid, tartaric acid, citric acid, Formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, Phthalic acid, isophthalic acid, glutaric acid, Gluconic acid, lactic acid, aspartic acid, Glutamic acid, itaconic acid, trifluoroacetic acid, Barbituric acid, cinnamic acid, benzoic acid, 4-hydroxybenzoic acid, aminobenzoic acid, etc., sulfonic acids, such as methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, Trifluoromethanesulfonic acid, styrenesulfonic acid, Naphthalenedisulfonic acid, hydroxybenzenesulfonic acid etc., polymeric acids such as polyacrylic or polymethacrylic acid and copolymers thereof (e.g., maleic acid-acrylic acid, Sulfonic acid-acrylic acid and styrene-acrylic acid copolymers), Carrageenoic acid, carboxymethylcellulose, alginic acid etc., etc. The total concentration of pH regulators can indeed vary, but these are typically in an amount of about 0.01% to about 10% by weight, in some embodiments from about 0.05% to about 5% by weight, and in some embodiments from about 0.1% to about 2% by weight of the electrolyte.

Of the Electrolyte can also contain other components that help the electrical efficiency of the capacitor too improve. For example, a depolarizer may be in the electrolyte be used to help the development of hydrogen gas to inhibit the cathode of the electrolytic capacitor, which otherwise could cause the capacitor to bulge out and finally failed. When he is employed, he does Depolarizer normally about 1 to about 500 ppm, in some embodiments from about 10 to about 200 ppm, and in some embodiments from about 20 to about 150 ppm of the electrolyte. To the appropriate Depolarizers include nitroaromatic compounds, such as 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2-nitroacetophenone, 3-nitroacetophenone, 4-nitroacetophenone, 2-nitroanisole, 3-nitroanisole, 4-nitroanisole, 2-nitrobenzaldehyde, 3-nitrobenzaldehyde, 4-nitrobenzaldehyde, 2-nitrobenzyl alcohol, 3-nitrobenzyl alcohol, 4-nitrobenzyl alcohol, 2-nitrophthalic acid, 3-nitrophthalic acid, 4-nitrophthalic acid etc. Particularly suitable nitroaromatic depolarizers for Use in the present invention are nitrobenzoic acids, Anhydrides or salts thereof containing one or more alkyl groups (eg, methyl, ethyl, propyl, butyl, etc.). Specific Examples of such alkyl-substituted nitrobenzo compounds are, for example, 2-methyl-3-nitrobenzoic acid, 2-methyl-6-nitrobenzoic acid, 3-methyl-2-nitrobenzoic acid, 3-methyl-4-nitrobenzoic acid, 3-methyl-6-nitrobenzoic acid, 4-methyl-3-nitrobenzoic acid, Anhydrides or salts thereof, etc. Without relying on a particular theory It is believed that alkyl-substituted nitrobenzo compounds preferably electrochemically at the active sites of the cathode surface can be adsorbed when the cathode potential a reached low range or the cell voltage is high, and then can be desorbed from this into the electrolyte, when the cathode potential goes up or the cell voltage low is. In this way, the compounds are "electrochemical reversible ", what an improved inhibition the hydrogen gas production can provide.

The anode of the electrolytic capacitor comprises a porous body which may be a valve metal composition having a high specific charge, such as 5000 μF * V / g or more, in some embodiments, about 25,000 μF * V / g or more, in some embodiments about 50,000 μF · V / g or more, and in some embodiments, from about 70,000 to about 300,000 μF · V / g. The valve metal composition includes a valve metal (ie, a metal capable of oxidation) or a valve metal based compound such as tantalum, niobium, aluminum, hafnium, titanium, alloys thereof, oxides thereof, nitrides thereof, etc. For example, the valve metal composition contain an electrically conductive oxide of niobium, such as niobium oxide having an atomic ratio of niobium to oxygen of 1: 1.0 ± 1.0, in some embodiments 1: 1.0 ± 0.3, in some embodiments 1: 1.0 ± 0.1 and in some embodiments 1: 1.0 ± 0.05. For example, the niobium oxide may be NbO _0.7 , Nb0 _1.0 , NbO _1.1 and NbO ₂ . Examples of such valve metal oxides are in the U.S. Patent Nos. 6,322,912 (Fife), 6,391,275 (Fife et al.), 6,416,730 (Fife et al.), 6,527,937 (Fife), 6,576,099 (Kimmel et al.), 6,592,740 (Fife et al.) And 6,639,787 (Kimmel et al.) And 7,220,397 (Kimmel et al.) And U.S. Patent Application Publication No. 2005/0019581 (Reapers), 2005/0103638 (Schnitter et al.), 2005/0013765 (Thomas et al.), All of which are expressly incorporated by reference for all purposes becomes.

In general, conventional manufacturing methods can be used to form the porous anode body. In one embodiment, a tantalum or niobium oxide powder having a certain particle size is first selected. The particles may be flaky, angular, nodular and mixtures or variations thereof. The particles also typically have a mesh size distribution of at least about 60 mesh, in some embodiments about 60 to about 325 mesh, and in some embodiments about 100 to about 200 mesh. Furthermore, the specific surface area is about 0.1 to about 10.0 m ² / g, in some embodiments about 0.5 to about 5.0 m ² / g, and in some embodiments about 1.0 to about 2.0 m ² /G. The term "specific surface area" refers to the specific surface area that after the physical gas adsorption process Brunauer, Emmet and Teller (BET), Journal of American Chemical Society, 60th year, 1938, p. 309 , is determined with nitrogen as the adsorption gas. Also, the bulk density (or Scott density) is typically about 0.1 to about 5.0 g / cm ^3, in some embodiments from about 0.2 to about 4.0 g / cm ^3, and in some embodiments from about 0.5 to about 3.0 g / cm ³ .

Around can facilitate the construction of the anode body also other components to the electrically conductive particles are given. For example, the electrically conductive Particles optionally with a binder and / or lubricant be mixed to ensure that the particles are sufficient adhere to each other when forming the anode body be pressed. Suitable binders include such as camphor, stearic or other soap fatty acids, Carbowax (Union Carbide), Glyptal (General Electric), polyvinyl alcohols, Naphthalene, vegetable wax and microwaxes (purified paraffins). The binder can be dissolved in a solvent and dispersed. Exemplary solvents are such as water, alcohols, etc. When used, the percentage may be the binder and / or lubricant from about 0.1 to about 8% by weight the total mass varies. One should, however, about it Be aware that binders and lubricants are present in the Invention are not required.

The resulting powder can be compacted using any conventional powder molding method. For example, the die may be a single-place compacting press that includes a die and one or more dies. Alternatively, anodising compacts of the anvil type using only a die and a single die can also be used. Single-station compacting dies are available in several basic types, such as cam, toggle and eccentric or crank presses with different capabilities, such as single-acting, double-acting, float mantle, moving platen, counter punch, auger, punch, hot press, stamp or calibrate. If desired, optional binder / lubricant may be removed after compression, such as by heating the formed compact in a vacuum for a few minutes (e.g., about 150 ° C to about 500 ° C) for several minutes. Alternatively, the binder / lubricant may also be removed by contacting the compact with an aqueous solution as described in U.S. Pat U.S. Patent No. 6,197,252 (Bishop et al.), Which is expressly incorporated by reference herein for all purposes.

The thickness of the pressed anode body may be relatively small, such as 4 millimeters or less, in some embodiments about 0.05 to about 2 millimeters, and in some embodiments about 0.1 to about 1 millimeter. The shape of the anode body can also be chosen so as to improve the electrical properties of the resulting capacitor. For example, the anode body may have a shape that is curved, wavy, rectangular, U-shaped, V-shaped, etc. The anode body may also have a "corrugated" shape by including one or more grooves, grooves, depressions or indentations to increase the surface to volume ratio thereby minimizing the equivalent series resistance (ESR) and extending the frequency response of the capacitance , Such "corrugated" anodes are for example in the U.S. Pat. Nos. 6,191,936 (Webber et al.), 5,949,639 (Maeda et al.) And 3,345,545 (Bourgault et al.) And US Patent Application Publication No. 2005/0270725 (Hahn et al.), to which reference is expressly made for all purposes.

The anode body may be anodized ("anodized") to form a dielectric layer on and / or within the anode. For example, a tantalum anode (Ta anode) can be anodized to tantalum pentoxide (Ta ₂ O ₅ ). Typically, the anodization is performed by first applying a solution to the anode, such as by immersing the anode in the electrolyte. Generally, a solvent is used, such as water (eg, deionized water). In order to enhance the ionic conductivity, a compound which can dissociate in the solvent to form ions can be used. Examples of such compounds are, for example, acids, as described above. For example, an acid (eg, phosphoric acid) may be from about 0.01% to about 5% by weight, in some embodiments from about 0.05% to about 0.8% by weight, and in In some embodiments, from about 0.1% to about 0.5% by weight of the anodizing solution. If desired, mixtures of acids may also be used.

One Current is passed through the anodizing solution to the to form a dielectric layer. The value of the formation voltage corresponds the thickness of the dielectric layer. For example, the power source may first be operated in the galvanostatic mode until the required Tension is reached. After that, the power source can be switched to a potentiostatic Mode to ensure that the desired thickness of the dielectric over the entire Surface of the anode is formed. Of course Other known methods can also be used. like potentiostatic pulse or stepping methods. The voltage, in which the anodic oxidation takes place, is typically in Range from about 4 to about 250 V, in some embodiments about 9 to about 200 V, and in some embodiments, about 20 to about 150 V. During the oxidation, the anodizing solution be kept at an elevated temperature, such as 30 ° C or more, in some embodiments, for example 40 ° C to about 200 ° C and in some embodiments about 50 ° C to about 100 ° C. The anodic oxidation Can also be done at ambient or below become. The resulting dielectric layer may be on a surface the anode and within their pores are formed.

The Cathode of the liquid electrolytic capacitor contains a metal substrate containing any metal, such as tantalum, niobium, aluminum, Nickel, hafnium, titanium, copper, silver, steel (eg stainless steel), Alloys thereof (eg electrically conductive oxides), Composites thereof (eg with electrically conductive oxide coated metal), etc. may contain. Titanium metals and alloys thereof are particularly suitable for use in the present invention well suited. The geometric configuration of the substrate can in general, as is well known to those skilled in the art, such as in the form of a container, cup, a foil, plate, Sieve, mesh, etc. The surface of the substrate may be in Range from about 0.05 to about 5 square centimeters, in some embodiments from about 0.1 to about 3 square centimeters, and in some embodiments about 0.5 to about 2 square centimeters.

A Coating of a conductive polymer is located also on the metal substrate. Without focusing on a specific theory wanting to commit, the inventors believe that charging the Capacitor to a high voltage (eg higher than the Formation stress) ions from the electrolyte into the polymer layer urges, which is due to the small wetting angle of aqueous Electrolytes in conductive polymer systems still promoted becomes. The movement of the ions causes the polymer to "swell" and the ions near the electrode surface holds back, which increases the charge density becomes. As the conductive polymer is generally amorphous and Non-crystalline, it can still be connected to the high voltage Dissipate and / or absorb heat. Furthermore It is assumed that the conductive polymer is "discharged" during the discharge Relaxed "and ions in the electrolyte from the polymer layer move out. Through this source and relaxation mechanism The charge density can be near the electrode without a chemical reaction with the electrolyte can be increased.

Generally speaking, conductive polymers are π-conjugated polymers that exhibit electrical conductivity after oxidation or reduction. Examples of such conductive polymers include, for example, polypyrroles, polythiophenes, polyanilines, polyacetylenes, poly-p-phenylenes (e.g., poly-p-phenylene sulfide or poly (p-phenylenevinylene)), polyfluorenes, polytetrathafulvenes, polynaphthalenes, derivatives of the above polymers , Mixtures thereof, etc. A particularly suitable class of conductive polymers are poly (alkylene thiophenes), such as poly (3,4-ethylenedioxythiophene) ("PEDT"). Various suitable conductive polymers are also known in the U.S. Patents 7,471,503 (Bruner et al.), 7,411,779 (Merker et al.), 7,377,947 (Merker et al.), 7,341,801 (Reuter et al.), 7,279,015 (Flag), 7,154,740 (Merker et al.), 6,987,663 (Merker et al.) And 4,910,645 (Jonas et al.), To which express reference is made for all purposes.

Other materials can also be used for a variety of purposes in the conductive polymer coating. For example, conductive fillers such as activated carbon, carbon black, graphite, etc. may be used to increase conductivity. Some suitable forms of activated carbon and techniques for their formation are in the U.S. Pat. Nos. 5,726,118 (Ivey et al.), 5,858,911 (Wellen et al.) And US Patent Application Publication No. 2003/0158342 (Shinozaki et al.), All of which are expressly incorporated herein by reference. At times, polymeric anions may be employed to form an antipode to any charge associated with the conductive polymer. The anions may be, for example, polymeric carboxylic acids such as polyacrylic acids, polymethacrylic acid or polymaleic acids, or polymeric sulfonic acids such as polystyrenesulfonic acids ("PSS") and polyvinylsulfonic acids. When employed, such polymeric anions and conductive polymers may be present in a weight ratio of from about 0.5: 1 to about 50: 1, in some embodiments from about 1: 1 to about 30: 1, and in some embodiments from about 2: 1 to about Be present 20: 1.

The conductive polymer may be applied to the metal substrate in the form of one or more layers and may be formed by a variety of known techniques. For example, techniques such as screen printing, dip coating, electrophoretic coating and spraying can be used to form the coating. For example, in one embodiment, the monomers used to form the conductive polymer (eg, PEDT) may be first mixed with a polymerization catalyst to form a dispersion. A suitable polymerization catalyst is CLEVIOS C (Bayer Corporation), which is iron (III) toluenesulfonate and n-butanol. CLEVIOS C is a commercially available catalyst for CLEVIOS M, which is 3,4-ethylenedioxythiophene, a PEDT monomer also marketed by Bayer Corporation. Once a dispersion is formed, the substrate can be immersed in the dispersion to form the conductive polymer. Alternatively, the catalyst and monomer (s) may also be applied separately. For example, the catalyst may be dissolved in a solvent (eg, butanol) and then applied as a dipping solution. Although various methods have been described above, it should be understood that any other method of applying the coating comprising the conductive polymer may be used. Other methods of applying such a coating comprising one or more conductive polymers are disclosed, for example, in U.S. Pat U.S. Pat. Nos. 5,457,862 (Sakata et al.), 5,473,503 (Sakata et al.), 5,729,428 (Sakata et al.) And 5,812,367 (Kudoh et al.), Which is hereby expressly incorporated by reference.

The physical arrangement of the anode, cathode and the electrolyte of the capacitor may generally vary as is well known in the art. In 1 For example, one embodiment is an electrolytic capacitor 40 shown a liquid electrolyte 44 which covers itself between an anode 20 and a cathode 43 located. The anode 20 contains a dielectric layer 21 and is with a connection 42 (eg tantai wire) embedded. The cathode 43 becomes from a substrate 41 as described above and a conductive polymer coating 49 educated. In this embodiment, the cathode substrate is located 41 in the form of a cylindrical "cup" with attached lid in front. A seal 23 (For example, glass-metal), which is the anode 20 with the cathode 43 connects and seals, can also be used. If desired, a separator (e.g., paper, plastic fibers, glass fibers, porous membranes, and ion permeable materials such as Nafion ^™ ) may be interposed between the cathode 43 and the anode 20 in order to prevent direct contact between the anode and the cathode and yet an ion current from the electrolyte 44 to allow for the electrodes.

The electrolytic capacitor of the present invention can be used in various applications; These include, but are not limited to, medical devices such as implantable defibrillators, pacemakers, cardioverter, nerve stimulators, drug delivery devices, etc., automotive applications, military applications such as RADAR systems, consumer electronics such as radios, televisions, etc., etc. In one embodiment, the capacitor For example, in an implantable medical device configured to provide for a therapeutic high voltage treatment of a patient (eg, between about 500 volts and about 850 volts, or desirably between about 600 volts and about 900 volts) ). The device may include a container or housing that is hermetically sealed and biologically inert. One or more terminals are electrically coupled via a wire between the device and the patient's heart. Heart electrodes are provided to monitor heart activity and / or apply voltage to the heart. At least a portion of the terminals (eg, an end portion of the terminals) may be provided near or in contact with a chamber and / or atrium of the heart. The device also includes a capacitor array, which typically includes two or more capacitors connected in series and coupled to a battery that is internally or externally disposed with respect to the device and the capacitor group provides energy. Partly due to the high conductivity, the capacitor of the present invention can achieve excellent electrical properties and thus be suitable for use in the capacitor array of the implantable medical device.

The The present invention will be better understood from the following examples understandable.

example 1

An electrolyte was formed by dissolving 10.65 grams of ammonium adipate (NH ₄ OC (O) (CH ₂ ) ₄ C (O) ONH ₄ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 2

One Electrolyte was formed as described in Example 1, except that 5.3 grams of ammonium adipate was used.

Example 3

One Electrolyte was formed as described in Example 1, except that 2.65 grams of ammonium adipate was used.

Example 4

An electrolyte was formed by dissolving 10.65 grams of ammonium adipate in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol, 0.1 grams of 3-methyl-4-nitrobenzoic acid ("MNBA") and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 5

One Electrolyte was formed as described in Example 4, except that 5.3 grams of ammonium adipate was used.

Example 6

One Electrolyte was formed as described in Example 4, except that 2.65 grams of ammonium adipate was used.

Example 7

An electrolyte was formed by dissolving 10.65 grams of ammonium acetate (NH ₄ OC (O) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 8

One Electrolyte was formed as described in Example 7, except that 5.3 grams of ammonium acetate were used.

Example 9

One Electrolyte was formed as described in Example 7, except that 2.65 grams of ammonium acetate was used.

Example 10

An electrolyte was formed by dissolving 10.65 grams of sodium acetate (NaOC (O) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 11

One Electrolyte was formed as described in Example 10 except that 5.3 grams of sodium acetate was used.

Example 12

One Electrolyte was formed as described in Example 10 except that 2.65 grams of sodium acetate was used.

Example 13

An electrolyte was formed by dissolving 5.3 grams of lithium acetate (LiOC (O) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 14

One Electrolyte was formed as described in Example 13 except that 2.65 grams of lithium acetate was used.

Example 15

An electrolyte was formed by dissolving 2.65 grams of lithium lactate (LiOC (O) CH (OH) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 16

An electrolyte was formed by dissolving 2 grams of ammonium oxalate (NH ₄ OC (O) C (O) ONH ₄ ) in 54 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 17

One Electrolyte was formed as described in Example 16 except that 1 gram of ammonium oxalate was used.

Example 18

One Electrolyte was formed as described in Example 16 except that 0.5 grams of ammonium oxalate was used.

Example 19

An electrolyte was formed by dissolving 2 grams of ammonium tartrate (NH ₄ OC (O) CH (OH) CH (OH) C (O) ONH ₄ ) in 54 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Example 20

One Electrolyte was formed as described in Example 19 except that 1 gram of ammonium tartrate was used.

Example 21

One Electrolyte was formed as described in Example 19 except that 0.5 grams of ammonium tartrate was used.

Example 22

An electrolyte was formed by dissolving 2.7 grams of disodium tartrate (NaOC (O) CH (OH) CH (OH) C (O) ONa) in 54 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO ₄ (85%) were added to the solution.

Testing the examples

Various Properties of the electrolytes of Examples 1-14 and 16-22 Were tested. In particular, a metal substrate was formed, by defatting a titanium mug and adding it to oxalic acid (10 wt .-% aqueous solution) etched, the Sheet dried and its inner surface with sandpaper and roughen a Dremel tool. The roughened surface was subsequently coated with PEDT polymer. The coating was applied by placing the titanium metal in a solution of CLEVIOS C in 1-butanol. After the CLEVIOS C applied was, the metal was immersed in CLEVIOS M and for 30 minutes placed in a box with controlled humidity and temperature. The relative humidity of the chamber ranged from 75 to 85%, and the temperature ranged from 22 ° C to 25 ° C. Thereafter, the coated metal was washed four times with methanol or ethanol washed to unpolymerized material and the remains of Baytron C to remove. The final drying step was also in a chamber with controlled humidity at one relative humidity of about 60%. The coating, washing and and drying steps were repeated four times to obtain a coating thickness of about 20 to 50 microns on the titanium metal to achieve.

Then The resulting cathode was immersed in the electrolyte. To test the electrolyte, it became a porous cylindrical one Tantalum body used as the anode, which is a formed at 205 V. Tantalum pentoxide dielectric contained. A polypropylene separator material was wetted with the electrolyte. The anode body was completely immersed in the electrolyte and then again withdrawn to secure the wetted separator material. With the separator around the anode, the assembly was placed in the electrolyte, before being placed in a vacuum oven for 15 minutes. Separately, the titanium cathode was made with 1 milliliter of the electrolyte filled. Thereafter, the anode with the separator in the Titanium cup brought. The arrangement was connected to a power source (Positive pole to the cylindrical anode and negative pole to the titanium cup) and a 1 kΩ resistor with one amperage charged in the range of 10 to 40 milliamps. The charging current influenced the load time, which was in the range of 4.3 seconds at 10 mA was up to 1.3 seconds at 40 mA. The arrangement was up to the Charged voltage set by the power source. After this the cell had been charged to the set voltage, she was held for several minutes with the charging current. Then The cell was discharged via a 100 Ω resistor.

The pH, voltage, charging time and discharge time were measured. The results are shown below in Tables 1 to 5. Table 1: Properties of Examples 1 to 6 Ex. salt % Ionenleitf. (mS / cm, 25 ° C) pH Voltage (V) Entladungskap. (Microfarads) Energy (J) Loading time (s) Discharge time (ms) 1 ammonium adipate 11.7 39.9 6.48 240 200 5.8 3.5 210 ₂ ammonium adipate 5.8 26.6 6.07 270 190 6.9 4.2 280 ₃ ammonium adipate 2.9 14.2 5.63 280 158 6.2 4.3 290 4 ammonium adipate 11.7 40.3 6.33 - - - - - ₅ ammonium adipate 5.8 26.5 5.93 270 200 7.3 4.0 180 ₆ ammonium adipate 2.9 13.9 5.57 280 195 7.6 4.2 210

Testing of the ammonium adipate electrolyte resulted in cells that could be charged to 280V. By comparison, it was determined that similar cells using 5MH ₂ SO ₄ as the electrolyte could only be charged to 140V. As indicated, lowering the amount of ammonium adipate in the electrolyte of the base formulation increased the stored potential energy. Furthermore, the ionic conductivity of the ammonium adipate electrolyte ranged from about 13.9 to 40.3 mS / cm, which was significantly less than the ionic conductivity of the 5-MH ₂ SO ₄ electrolyte (about 1000 mS / cm). Table 2: Properties of Examples 7 to 9 Ex. salt % Ionleltf (mS / cm, 25 ° C) pH Voltage (V) Entladungskap. (Microfarads) Energy (J) Loading time (s) Discharge time (ms) 7 ammonium acetate 11.7 39.0 6.07 230 190 5.0 1.0 152 _8th ammonium acetate 5.8 26.0 5.86 250 180 5.6 1.0 184 ₉ ammonium acetate 2.9 14.9 5.48 280 180 7.1 1.3 204

The ammonium acetate electrolytes showed similar behavior to the ammonium adipate electrolytes of Examples 1 to 6. Table 3: Properties of Examples 10 to 14 Ex. salt % Ionenleltf. (mS / cm, 25 ° C) pH Voltage (V) Entladungskap. (Microfarads) Energy (J) Loading time (s) Discharge time (ms) 10 sodium 11.7 26.0 6.14 150 180 2.0 0.9 128 11 sodium 5.8 18.2 6.04 210 190 4.2 0.9 152 12 sodium 2.9 8.6 4.94 250 190 5.9 1.1 184 13 lithium 5.8 10.3 5.24 230 195 5.2 1.0 162 14 lithium 2.9 5.8 5.12 280 210 8.2 1.4 230

The sodium and lithium acetate electrolytes behaved similarly to the ammonium adipate electrolytes of Examples 1-6. Table 4: Properties of Examples 16-21 Ex. salt % Ionleltf (mS / cm, 25 ° C) pH Voltage (V) Entladungskap. (Microfarads) Energy (J) Loading time (s) Discharge time (ms) 16 ammonium oxalate 2.4 6.8 4.5 290 200 8.4 - - 17 ammonium oxalate 1.2 4.3 4.5 290 200 8.4 - - 18 ammonium oxalate 0.6 2.3 4.0 290 200 8.4 - - 19 ammonium tartrate 2.4 9.1 4.7 280 200 7.8 - - 20 ammonium tartrate 1.2 5.1 4.4 290 200 8.4 - - 21 ammonium tartrate 0.6 2.7 3.8 270 200 7.3 - -

As indicated, the ammonium oxalate and tartrate electrolytes were readily charged to voltages up to 290V. Presumably such high voltages have been achieved because the solubility limit of the ammonium salts of oxalic acid and tartaric acid is low, and therefore the maximum concentration in the electrolyte is limited. Table 5: Properties of Example 22 Ex. (MS / cm, salt % Ionenleltf. (mS / cm, 25 ° C) pH Voltage (V) Entladungskap. (Microfarads) Energy (J) Loading time (s) Discharge time (ms) 22 sodium tartrate 2.9 6.8 4.6 280 200 7.8

Of the Sodium tartrate electrolyte showed a similar behavior like the ammonium tartrate electrolytes of Examples 19 to 21.

• 1. Flüssigelektrolytkondensator, umfassend: einen porösen Anodenkörper, der eine durch anodische Oxidation gebildete dielektrische Schicht enthält; eine Kathode, die ein Metallsubstrat umfasst, das mit einem leitfähigen Polymer beschichtet ist; und einen wässrigen Elektrolyten, der sich in Kontakt mit der Kathode und der Anode befindet, wobei der Elektrolyt ein Salz einer schwachen organischen Säure und Wasser umfasst, wobei der Elektrolyt einen pH-Wert von etwa 4,5 bis etwa 7,0 und eine Ionenleitfähigkeit von etwa 0,1 bis etwa 30 Millisiemens pro Zentimeter hat, bestimmt bei einer Temperatur von 25°C.
• 2. Flüssigelektrolytkondensator gemäß Punkt 1, wobei der Elektrolyt eine Ionenleitfähigkeit von etwa 1 bis etwa 20 Millisiemens pro Zentimeter hat, bestimmt bei einer Temperatur von 25°C.
• 3. Flüssigelektrolytkondensator gemäß Punkt 1 oder 2, wobei der pH-Wert etwa 5,0 bis etwa 6,5 beträgt.
• 4. Flüssigelektrolytkondensator gemäß Punkt 1 bis 3, wobei das Salz ein einatomiges Kation enthält.
• 5. Flüssigelektrolytkondensator gemäß Punkt 4, wobei das einatomige Kation ein Alkalimetallion ist.
• 6. Flüssigelektrolytkondensator gemäß Punkt 1 bis 3, wobei das Salz ein mehratomiges Kation enthält.
• 7. Flüssigelektrolytkondensator gemäß Punkt 6, wobei das mehratomige Kation ein Ammoniumion ist.
• 8. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei die organische Säure eine erste Säuredissoziationskonstante von etwa 2 bis etwa 10 hat, bestimmt bei einer Temperatur von 25°C.
• 9. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei die organische Säure eine Carbonsäure ist.
• 10. Flüssigelektrolytkondensator gemäß Punkt 9, wobei die Carbonsäure polyprotisch ist.
• 11. Flüssigelektrolytkondensator gemäß Punkt 10, wobei es sich bei der polyprotischen Carbonsäure um Adipinsäure, Weinsäure, Oxalsäure, Zitronensäure oder eine Kombination davon handelt.
• 12. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei Salze einer schwachen organischen Säure etwa 0,1 bis etwa 25 Gew.-% des Elektrolyten ausmachen.
• 13. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei Salze einer schwachen organischen Säure etwa 0,3 bis etwa 15 Gew.-% des Elektrolyten ausmachen.
• 14. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei Wasser etwa 20 bis etwa 95 Gew.-% des Elektrolyten ausmacht.
• 15. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei der Elektrolyt weiterhin ein sekundäres Lösungsmittel umfasst.
• 16. Flüssigelektrolytkondensator gemäß Punkt 15, wobei das sekundäre Lösungsmittel Ethylenglycol umfasst.
• 17. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei das Metallsubstrat Titan umfasst.
• 18. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei das leitfähige Polymer ein Polythiophen ist.
• 19. Flüssigelektrolytkondensator gemäß Punkt 18, wobei es sich bei dem Polythiophen um Poly(3,4-ethylendioxythiophen) oder ein Derivat davon handelt.
• 20. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei der Anodenkörper aus Tantal oder aus Nioboxid besteht.
• 21. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei das Verhältnis der Spannung, bis zu der der Kondensator aufgeladen werden kann, zur Spannung, bei der die dielektrische Schicht gebildet wird, etwa 1,0 bis 2,0 beträgt.
• 22. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei die Spannung, bis zu der der Kondensator aufgeladen werden kann, etwa 200 bis etwa 350 V beträgt.
• 23. Flüssigelektrolytkondensator gemäß einem der obigen Punkte, wobei die Spannung, bis zu der der Kondensator aufgeladen werden kann, etwa 250 bis etwa 300 V beträgt.
• 24. Flüssigelektrolytkondensator, umfassend: einen porösen Anodenkörper, der aus Tantal oder aus Nioboxid besteht, wobei der Anodenkörper weiterhin eine durch anodische Oxidation gebildete dielektrische Schicht enthält; e ine Kathode, die ein Titansubstrat umfasst, das mit einem leitfähigen Polymer beschichtet ist, wobei das leitfähige Polymer Poly(3,4-ethylendioxythiophen) oder ein Derivat davon umfasst; und einen wässrigen Elektrolyten, der sich in Kontakt mit der Kathode und der Anode befindet, wobei der Elektrolyt ein Salz einer schwachen organischen Säure und Wasser umfasst, wobei der Elektrolyt einen pH-Wert von etwa 4,0 bis etwa 7,0 und eine Ionenleitfähigkeit von etwa 0,5 bis etwa 25 Millisiemens pro Zentimeter hat, bestimmt bei einer Temperatur von 25°C.
• 25. Flüssigelektrolytkondensator gemäß Punkt 24, wobei der Elektrolyt eine Ionenleitfähigkeit von etwa 1 bis etwa 20 Millisiemens pro Zentimeter hat, bestimmt bei einer Temperatur von 25°C.

These and other modifications and variations of the present invention may be practiced by those skilled in the art without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be partially or completely interchanged. Furthermore, those skilled in the art will recognize that the above description is merely exemplary in nature and is not intended to limit the invention, which is further described in the appended claims.

• A liquid electrolytic capacitor comprising: a porous anode body containing a dielectric layer formed by anodic oxidation; a cathode comprising a metal substrate coated with a conductive polymer; and an aqueous electrolyte in contact with the cathode and the anode, wherein the electrolyte comprises a salt of a weak organic acid and water, wherein the electrolyte has a pH of about 4.5 to about 7.0 and an ionic conductivity from about 0.1 to about 30 millisiemens per centimeter, determined at a temperature of 25 ° C.
• 2. The liquid electrolytic capacitor according to item 1, wherein the electrolyte has an ionic conductivity of about 1 to about 20 millisiemens per centimeter, determined at a temperature of 25 ° C.
• 3. The liquid electrolytic capacitor according to item 1 or 2, wherein the pH is about 5.0 to about 6.5.
• 4. The liquid electrolytic capacitor according to item 1 to 3, wherein the salt contains a monatomic cation.
• 5. The liquid electrolytic capacitor according to item 4, wherein the monatomic cation is an alkali metal ion.
• 6. The liquid electrolytic capacitor according to item 1 to 3, wherein the salt contains a polyatomic cation.
• 7. A liquid electrolytic capacitor according to item 6, wherein the polyatomic cation is an ammonium ion.
• 8. The liquid electrolytic capacitor according to any one of the above items, wherein the organic acid has a first acid dissociation constant of about 2 to about 10, determined at a temperature of 25 ° C.
• 9. A liquid electrolytic capacitor according to any one of the above items, wherein the organic acid is a carboxylic acid.
• 10. A liquid electrolytic capacitor according to item 9, wherein the carboxylic acid is polyprotic.
• 11. The liquid electrolytic capacitor according to item 10, wherein the polyprotic carboxylic acid is adipic acid, tartaric acid, oxalic acid, citric acid or a combination thereof.
• 12. A liquid electrolytic capacitor according to any one of the above, wherein salts of a weak organic acid make up about 0.1 to about 25% by weight of the electrolyte.
• A liquid electrolytic capacitor according to any one of the above, wherein salts of a weak organic acid constitute from about 0.3 to about 15% by weight of the electrolyte.
• 14. The liquid electrolytic capacitor according to any one of the above, wherein water is about 20 to about 95% by weight of the electrolyte.
• 15. A liquid electrolytic capacitor according to any one of the above, wherein the electrolyte further comprises a secondary solvent.
• 16. A liquid electrolytic capacitor according to item 15, wherein the secondary solvent comprises ethylene glycol.
• 17. A liquid electrolytic capacitor according to any one of the above, wherein the metal substrate comprises titanium.
• 18. A liquid electrolytic capacitor according to any one of the above items, wherein the conductive polymer is a polythiophene.
• 19. A liquid electrolytic capacitor according to item 18, wherein the polythiophene is poly (3,4-ethylenedioxythiophene) or a derivative thereof.
• 20. A liquid electrolytic capacitor according to any of the above items, wherein the anode body is tantalum or niobium oxide.
• 21. A liquid electrolytic capacitor according to any one of the above, wherein the ratio of the voltage until to which the capacitor can be charged to the voltage at which the dielectric layer is formed is about 1.0 to 2.0.
• 22. The liquid electrolytic capacitor according to any one of the above, wherein the voltage to which the capacitor can be charged is about 200 to about 350 volts.
• 23. The liquid electrolytic capacitor according to any one of the above, wherein the voltage to which the capacitor can be charged is about 250 to about 300 volts.
• 24. A liquid electrolytic capacitor comprising: a porous anode body made of tantalum or niobium oxide, said anode body further containing a dielectric layer formed by anodic oxidation; a cathode comprising a titanium substrate coated with a conductive polymer, the conductive polymer comprising poly (3,4-ethylenedioxythiophene) or a derivative thereof; and an aqueous electrolyte in contact with the cathode and the anode, wherein the electrolyte comprises a salt of a weak organic acid and water, the electrolyte having a pH of from about 4.0 to about 7.0 and an ionic conductivity from about 0.5 to about 25 millisiemens per centimeter, determined at a temperature of 25 ° C.
• 25. The liquid electrolytic capacitor according to item 24, wherein the electrolyte has an ionic conductivity of from about 1 to about 20 millisiemens per centimeter, determined at a temperature of 25 ° C.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

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Claims (16)

A liquid electrolytic capacitor, comprising: one porous anode body, the one by anodic Oxidation formed dielectric layer contains; a Cathode, which includes a metal substrate, which is conductive with a Polymer is coated; and an aqueous electrolyte, which is in contact with the cathode and the anode, wherein the electrolyte is a salt of a weak organic acid and water, wherein the electrolyte has a pH of about 4.5 to about 7.0 and an ionic conductivity of about 0.1 to about 30 millisiemens per centimeter, determined at one Temperature of 25 ° C. Liquid electrolytic capacitor according to claim 1, wherein the electrolyte has an ionic conductivity of about 1 to about 20 millisiemens per centimeter, determined at one Temperature of 25 ° C. Liquid electrolytic capacitor according to claim 1 or 2, wherein the pH is about 5.0 to about 6.5. Liquid electrolytic capacitor according to claim 1 to 3, wherein the salt is a monatomic cation, such as an alkali metal ion, contains. Liquid electrolytic capacitor according to claim 1 to 3, wherein the salt is a polyatomic cation, such as an ammonium ion, contains. Liquid electrolytic capacitor according to a of the preceding claims, wherein the organic acid is a first acid dissociation constant of about 2 to about 10 has, determined at a temperature of 25 ° C. Liquid electrolytic capacitor according to a of the preceding claims, wherein the organic acid is a Carboxylic acid is. Liquid electrolytic capacitor according to claim 7, wherein the carboxylic acid is a polyprotic acid, such as adipic acid, tartaric acid, oxalic acid, Citric acid or a combination thereof. Liquid electrolytic capacitor according to a of the preceding claims, wherein salts of a weak organic Acid about 0.1 to about 25 wt .-%, and preferably about Make up 0.3 to about 15 wt .-% of the electrolyte. Liquid electrolytic capacitor according to a of the preceding claims, wherein water is about 20 to about 95 wt .-% of the electrolyte. Liquid electrolytic capacitor according to a of the preceding claims, wherein the metal substrate is titanium includes. Liquid electrolytic capacitor according to a of the preceding claims, wherein the conductive Polymer is a polythiophene, such as poly (3,4-ethylenedioxythiophene) or a derivative thereof. Liquid electrolytic capacitor according to a of the preceding claims, wherein the anode body of Tantalum or niobium oxide. Liquid electrolytic capacitor according to a of the preceding claims, wherein the ratio the voltage up to which the capacitor can be charged to the voltage at which the dielectric layer is formed, such as 1.0 to 2.0. Liquid electrolytic capacitor according to a of the preceding claims, wherein the tension, up to the the capacitor can be charged, about 200 to about 350 volts and preferably about 250 to about 300 volts. A liquid electrolytic capacitor comprising: a porous anode body made of tantalum or niobium oxide, said anode body further containing a dielectric layer formed by anodic oxidation; a cathode comprising a titanium substrate coated with a conductive polymer, the conductive polymer comprising poly (3,4-ethylenedioxythiophene) or a derivative thereof; and an aqueous electrolyte in contact with the cathode and the anode, the electrolyte comprising a salt of a weak organic acid and water, the electrolyte having a pH of from about 4.0 to about 7.0 and an ionic conductivity of about 0.5 to about 25 millisiemens per centimeter, determined at a temperature of 25 ° C.